Manufacturers often optimize the designs of parts that they manufacture in efforts to increase the efficiencies of devices and structures in which the parts are used. Designs are often optimized through the use of light-weight materials and by the minimization of the amounts of materials used.
For example, in order to reduce weight of aircraft components, manufacturers typically design skeletal frames enclosed by thin skins utilizing light-weight materials such as aluminum, titanium, and silicon. In order for these components to perform as intended, the components must be manufactured without surface irregularities and without hidden flaws. If surface irregularities and flaws hidden below the surface of a component go undetected, the component may fail. Therefore such components are typically subjected to careful inspections both prior to use and during the service life of the components.
Aircraft components made of light-weight composite materials are further examples of parts that are routinely subjected to inspection. Composite materials are commonly used because of their engineering qualities, design flexibilities, and low weights. However, a component constructed of a composite material may have flaws both at the surface and below the surface of the material. Surface irregularities such as scratches and holes and more hidden irregularities such as cracks, voids, disbonds, and hidden porosities may greatly compromise the strength and durability of a composite component.
Complicating the inspection of aircraft components and parts for other assemblies is the fact that optimized designs often include complex geometries, curved surfaces, and limited access spaces. For example, a typical aircraft fuselage stringer can be over one hundred feet long, and typically partially encloses an elongate space having a trapezoidal cross-section that may be merely a foot wide. Aircraft wings typically have internal features, bond lines, and close-out joints that further exemplify designs having complex geometries and limited access spaces. Limited-access spaces, such as those enclosed by close-out joints of aircraft wings, are difficult to fully inspect using contemporary inspection devices.
Thus, as typical design optimization processes rely on the assumption that parts are manufactured to exacting specifications, manufacturers face a difficult challenge in identifying parts that fail to meet specifications while controlling manufacturing and maintenance costs. Non-destructive inspection (NDI) devices and techniques provide for inspections and evaluations of fully or partially assembled parts without compromising the parts.
NDI typically involves thoroughly examining a structure without harming the structure or requiring significant disassembly of the structure. NDI is advantageous for many applications in which thorough inspections of the exteriors and interiors of structures are desired. NDI is commonly utilized in the aircraft industry for inspecting aircraft components for internal or external structural damages. Composite components, critical structural components, and light-weight components of aircraft structures are often subjected to NDI to identify surface irregularities and hidden flaws.
A need exists for convenient and reliable NDI devices that are capable detecting flaws defined in the surface of a component and flaws below the surface of the component. A need exists for NDI devices that are capable of inspecting limited-access features of a structure. A need exists for NDI devices that facilitate visual inspections of structural surfaces in conjunction with inspection techniques that reveal hidden flaws.